Hadron formation in a nuclear environment at HERMES Original Research Article

The influence of the nuclear medium on the production of charged hadrons has been studied by the HERMES experiment at DESY in semi-inclusive deep inelastic scattering of 27.5 GeV positrons off deuterium, nitrogen and krypton targets. The differential multiplicity from the nucleus relative to that from the deuterium has been measured for charged hadrons and, for the first time, for identified pions, kaons, protons and antiprotons as a function of the relevant kinematic variables: the virtual photon energy v, the fraction z of this energy transferred to the hadron and the hadron transverse momentum squared View the MathML source. The multiplicity ratio View the MathML source is strongly reduced at low v and high z with significant differences for different hadrons. The distribution of the hadron transverse momentum is broadened at high View the MathML source in the nuclear medium showing the evidence of the Cronin effect in the deep inelastic scattering process.